The benefits of "isometric" abdominal muscle training are well recognized. In a well known approach, a highly trained athlete manually reciprocates a simple abdominal roller or wheel across a floor surface by kneeling and extending and retracting his body.
However, not only does a relatively untrained person usually not have the initial strength, particularly in the wrists and lower back, to perform such exercise, but the exercise involves the same repetitive action whereas the most effective way to train a muscle group for continual improvement is to perform a variety of different exercises.
U.S. Pat. No. 4,930,769 issued in 1990 to Nenoff teaches an exercise apparatus providing a seat on a track along which a user advances his body by only a pull/push arm action while supported by the seat. The inclination of the track can be changed to alter the effort required. However, this apparatus is intended, primarily, to exercise muscles of the arms and back.
U.S. Pat. No. 5,499,961 issued 1996 to Mattox and U.S. Pat. No. 5,518,483 issued 1996 to Oswald both teach exercise apparatus of the push-pull type for exercising the abdominal muscle set in which the user manually reciprocates a hand grip device along a track by extending and retracting his body between kneeling and prone positions while resting his knees on a knee support.
However, although teaching variable resistance means, the latter two references do not teach means for reducing the effort of the user particularly ameliorating stress on the wrists and lower back. Furthermore, the exercise permitted by the apparatus still involves essentially the same repetitive movement.